The disclosed apparatus and method provides a efficient, low cost system for more accurate digitized image coverage area sampling for use in an electronic printers, copiers computers or other electronic imaging device. In particular, the apparatus and method of the present invention are highly useful to predict imaging ink/toner and other consumable material depletion, service and maintenance requirements in a printer or copier.
As will be further described herein, the digitized image sampling system of the present invention can accurately estimate cumulative pixel "on" or "activated" totals in a data stream, so as to predict, estimate and/or manage, for example, toner/ink usage in printers, copiers or other electronic imaging devices (hereinafter, "printers"). The disclosed system can be utilized with any printer, to reduce sensor physical condition costs, improve printer reliability, or other reasons. The disclosed exemplary system is an improvement over other pixel (image bit or byte) counting methods that might be used to determine print engine ink/toner usage and/or to measure or monitor other aspects of printing operations.
A feature of specific embodiments of the present invention disclosed herein is to provide an improved system for accurately estimating consumption of imaging materials (inks, toners, carriers, oils, etc.) as well as service and maintenance requirements in a printer that can be measured or predicted in relation to the digital pixels which are being used to generate the various images in a data (byte) stream. Unlike a system that might unsuccessfully avoid errors caused by image patterns, repetitive effects, byte/pixel frequency sets or other data or pixel stream artifacts that can result in inaccurate pixel estimations or determinations, the present system limits if not eliminates the occurrence such errors. Even when digitally compressed images are sampled, the system of the present invention can permit accurate analysis of the sampled pixels in the data stream. Devices and methods of pixel on/off weighing, gray scale/halftone detection and other systems rely on pixel counting system total image pixel count systems. By way of background, pending Xerox Corporation U.S. application Ser. No. 08/062,971, now U.S. Pat. No. 5,349,377, filed May 17, 1993 (D/93150), entitled, "Printer Toner Usage Indicator With Image Weighted Calculation ", by Keith Gilliland, et al. and disclosures cited therein, are directed to such systems that rely on pixel counting and/or frequency monitoring in applying weighing factors in making toner use determinations.
The following disclosures may be relevant to various aspects of the present invention:
U.S. Pat. No. 5,204,699
Patentee: Birnbaum et al.
Issued: Apr. 20, 1993
U.S. Pat. No. 5,204,698
Patentee: LeSueur et al.
Issued: Apr. 20, 1993
U.S. Pat. No. 4,908,666
Patentee: Resch, III
Issued: Mar. 13, 1990
U.S. Pat. No. 4,847,659
Patentee: Resch, III
Issued: Jul. 11, 1989
U.S. Pat. No. 4,468,112
Patentee: Suzuki et al.
Issued: Aug. 28, 1984
U.S. Pat. No. 3,409,901
Patentee: M. H. Dost et al.
Issued: Nov. 5, 1968
EP-0 526 197 A2
Patentee: Huttenlocher et al.
Published: Mar. 2, 1993
GB-2 153 619 A
Patentee: M. H. Dost et al.
Issued: Aug. 21, 1985
"Random Sample Consensus: A Paradigm for Model Fitting with Applications to Image Analysis and Automated Cartography,"
Authors: M. A. Fischler and R. C. Bolles Communications of the ACM, Vol. 24, No. 6, June 1981, pp. 381-395.
The relevant portions of the foregoing disclosures may be briefly summarized as follows:
U.S. Pat. No. 5,204,699 discloses an apparatus and method adaptable for use in a printing system, to measure the mass of toner developed on an electrostatic latent image produced therein. Toner usage of a printer is approximated as a function of the gray scale value of the image signal used to generate a pixel. The toner mass measuring apparatus sums a plurality of individual toner mass signals, generated as a function of the image intensity signals, to approximate the toner mass used to develop the electrostatic latent image. The particular function employed may be linear or nonlinear, depending upon the xerographic engine characteristics. The system herein can also be used with, or incorporate, said additional weighting for said assigned gray scale value, where the printer is one in which the pixels do have a (varying) gray scale value.
U.S. Pat. No. 5,204,698 discloses a laser printer in which a latent image is generated on a circulating imaging member in accordance with digital image signals and subsequently developed with toner, the number of pixels to be toned is used as an indication of the rate at which toner is being depleted from the developer mixture. The device for dispensing fresh toner to the developer mixture is operated in dependence on the number of pixels to be toned, according to a pixel counter. If toner dispensing efficiency falls, the preestablished relationship is adjusted so that the toner density in the developed images remains constant. If a predetermined level of adjustment is reached, it is taken as an indication that the supply of toner in the printer is low, and should be replenished.
U.S. Pat. No. 4,908,666 discloses a toner replenishment control structure for developer materials, in which two toner types are employed. On toner type exhibits toning contrast characteristics which vary predictably with the concentration of toner particles in the developer mix, while the other toner type does not exhibit predictable changes in toning contrast as the toner concentration changes. An electrostatographic machine produces a contrast signal having a value proportional to toning contrast and a concentration signal having a value indicative of the ratio of toner to carrier in the mix, the concentration signal being substantially insensitive to the toning contrast. The system actuates replenishment of toner of the first type according to the value of the contrast signal and actuates replenishment of toner of the second type according to the value of said concentration signal.
U.S. Pat. No. 4,847,659 discloses an electrostatographic machine which replenishes the toner in a developer mix proportionally in response to a toner depletion signal having a value indicative of the rate of toner usage. A second signal is produced having a value proportional to toning contrast; and the contrast of proportionality between toner replenishment and the depletion signal is adjusted in response to the second signal value. A toner replenishment controller determines toner usage according to indicative counted pages, characters or pixels to be toned.
U.S. Pat. No. 4,468,112 discloses a device for controlling the developer concentration in an electrophotographic copier or the like in which one detector determines developer concentration and a second detector that determines image density are utilized for controlling process devices such as toner dispensers to maintain a printed image density.
U.S. Pat. No. 3,409,901 discloses a xerographic system in which toner is dispensed according to print density and area. A cathode ray tube beam current, proportional to print density and area, drives a toner concentration control system which feeds toner to the developing mechanism. When the beam current exceeds a threshold, a batch of toner is released to the developer mechanism and the system is reset. A predetermined batch size may be made variable such that when the toner level in the feed box is high, the threshold which must be exceeded is relatively high, while if the toner level is low the threshold which must be exceeded is relatively low.
EP-0 526 197 A2, based on pending U.S. application Ser. No. 07/737,956 filed Jul. 30, 1991, discloses an image processing method wherein random or pseudo-random sampling is used to analyze an image to determine attributes such as skew, typeface, and character size and spacing. The number of sampled locations is smaller than the number of locations on the page but must be statistically significant. For example, 1000 samples may be required to determine skew or font, while 5000 samples may be sufficient to measure horizontal or vertical distances. Images may be segmented for characteristic measurement, such as for words or paragraphs.
GB 2 153 619A discloses an image processing apparatus capable of image discrimination, such as to produce accurate half-tone or picture image data. Generally, a threshold is applied to the image data at a certain level, and subsequent to thresholding the number of transitions from light to dark within a small area (block) is counted. The system operates on the presumption that data with a low number of transitions after thresholding is probably a high frequency halftone or continuous tone image. In one embodiment, image data is processed in 8.times.8 blocks; the density of each pixel is "binarized," and the transitions of neighboring pixels is summed. The summed value is compared to predetermined values to discriminate the nature of the image. If the sum is below the low value, it is dithered; if between the values, it is passed without processing; if above the higher value, it is discriminated as a dot image area, and its block pixel densities are averaged and coded. Other embodiments present variations of this process.
The publication by Fischler and Bolles discloses a paradigm capable of interpreting/smoothing data containing gross errors for applications in automated image analysis. The disclosed Random Sample Consensus paradigm may be applied to the image location determination problem, such as may be encountered in automated cartography applications, scanner/image analysis and the like.